Sophia pushes with a 40-N horizontal force on a 4.0-kg box resting on a lab bench. The box slides against a horizontal friction force of 24 N. show that the box acceleration at 4.0 m/s2

   a = 4.0 m / s²,     so the result of the exercise is correct

Explanation:

This is an exercise on Newton's Second Law

               F = m a

we create a reference system with the horizontal x axis and the vertical y axis

Axis y

             N -W = 0

X axis

              F -fr = m a

give us the applied force F = 40 N, the value of the friction outside fr = 24 N

               a = (F - fr) / m

let's calculate

              a = (40 - 24) / 4

              a = 4.0 m / s²

so the result of the exercise is correct

12000j is work done

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.